1. Field of the Invention
The present invention relates to an X-ray topography apparatus, and more particularly, to an X-ray topography apparatus using a multilayer mirror.
2. Description of the Related Art
An X-ray topography apparatus is an apparatus for observing, as an X-ray diffraction image, various crystal defects such as dislocations and precipitation in a single crystal, which are hard to observe when using general optical means. A diffraction phenomenon occurs when a sample crystal is placed so that lattice planes having a plane spacing “d” satisfy the Bragg's law “2d·sin θn=nλ” with respect to a wavelength “λ” of an incident X-ray. When the above-mentioned crystal defects are present within an irradiation region of the incident X-ray, the X-ray diffraction image has a difference in intensity between the crystal defect portion and the other portion. The X-ray diffraction image obtained by detecting the difference in intensity through use of a detector is referred to as “X-ray topographic image”.
The X-ray topography apparatus uses the Lang method, the Berg-Barrett method, the double crystal method, and other methods. The Lang method is a method of examining a distribution of defects in a crystal through imaging in the transmission geometry, and is most widely used thus far. The Berg-Barrett method is a method of examining and observing a crystal surface through imaging in the reflection geometry. The double crystal method is a method of diffracting an X-ray emitted from an X-ray source on a first crystal to obtain a monochromatized and collimated X-ray beam, which is caused to enter a sample crystal as a second crystal. The conventional X-ray topography apparatus uses a fine-focus X-ray source which may be regarded as a point X-ray source, and has a slit arranged between the X-ray source and the sample. With this structure, the angle of divergence of the X-ray which enters the sample is restricted, to thereby obtain a substantially collimated X-ray.